infocmp -C: only mark verbatim caps ".." when they use params/arithmetic/conditionals

The ".." obsolete marker is not applied to every untranslatable cap -- only to those
whose value references a parameter or uses arithmetic/conditional ops
(%p/%+/%-/%*/%?/%t/%e/%;). Caps that merely use dynamic-variable or bitwise exotica
(%g/%P/%^/%{/unknown, e.g. icl6402 se, qvt119 is) are copied through verbatim WITHOUT
the marker, matching ncurses (perfect correlation on %p; %+/%- add the arithmetic
cases like c108 ts).

Termcap (-C) content 65.8% -> 66.3%, exact 32.7%. terminfo -1 100%; tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CbiPgWC3PHKmrTNvZzXcWQ

Author: claude

crates/ncurses-tools/src/bin/infocmp.rs

@@ -462,11 +462,16 @@ fn me_from_sgr0(ti: &Terminfo) -> Option<Vec<u8>> {
     }
 }
 
-/// Build a termcap field `code=value`, prefixed with `..` when the value was kept verbatim
-/// (untranslatable param ops): ncurses marks such caps obsolete/unusable by old termcap readers.
+/// Build a termcap field `code=value`. A value kept verbatim (untranslatable) is prefixed with `..`
+/// only when it references a parameter or uses arithmetic/conditional ops (`%p`/`%+`/`%-`/`%*`/`%?`/
+/// `%t`/`%e`/`%;`): ncurses marks such caps obsolete, but copies through non-parameterized exotica
+/// (`%g`/`%P`/`%^`/`%{`/unknown ops) unmarked.
 fn tc_field(code: &str, raw: &[u8]) -> String {
     let (val, verbatim) = tc_xlat(raw);
-    let prefix = if verbatim { ".." } else { "" };
+    let marks_obsolete = raw
+        .windows(2)
+        .any(|w| w[0] == b'%' && matches!(w[1], b'p' | b'+' | b'-' | b'*' | b'?' | b't' | b'e' | b';'));
+    let prefix = if verbatim && marks_obsolete { ".." } else { "" };
     format!("{prefix}{code}={val}")
 }